The immediate aim of this research is the development of complementary cell biological strategies for cellular and sub-cellular fractionation of embryonic nervous tissue for the purpose of investigating the process of phenotypic expression and the cellular distribution of neuronal functions. During the past year embryonic elements dissected from the mammalian central nervous system have been studied using a variety of techniques, including dissociated primary and clonal cell culture, flow cytometry and fluorescence-activated cell and organelle sorting, immunohistochemistry with surface-reactive and transmitter-related reagents, light- and electron-microscopy, and intact-cell ligand binding. Preliminary protocols have been developed for analyzing in a quantitative manner subpopulations of cells by flow cytometry and for isolating specific cell types both for biochemical characterization and for potential use as immunogenic material, as well as for maintenance in culture. Principal findings include: 1) enzymatic digestions of embryonics CNS tissue yield maximal number of viable elements; 2) putative motoneurons and a subset of sensory cells can be back-filled and isolated; and 3) a subpopulation of embryonic spinal cord cells that synthesize GABA-related marker enzyme can be stained with a surface-reactive immunoreagent and isolated in cell culture. Distinguishing cellular properties have been revealed in these isolated sub-populations, indicating that studying the processes underlying phenotypic differentiation may be feasible with this combined flow-cytometric/cell-culture strategy.